- Subjects who answer affirmatively to any of the following questions on the Study Entry Questionnaire: (1) Do you have any medical condition that may make your body unable to fight infections like leukemia, lymphoma, human immunodeficiency virus (HIV), or organ transplant? (2) Over the last 4 weeks have you been treated for cancer and/or for autoimmune diseases; (3) Have you ever taken natalizumab, rituximab, or efalizumab, alemtuzumab, and mycophenolate, or any immunosuppressive agent known to be associated with Progressive Multifocal Leukoencephalopathy (PML)? (4) Have you taken any of the following medicines over the last 12 months: dexamethasone, bethamethasone, methylprednisolone, budesonide, prednisone, methotrexate, cyclosporine, tacrolimus, enbrel, humira, remicade, azathioprine, 6-MP, chemotherapy-related drugs, anti-tumor necrosis factor (TNF) alpha agents, or any immunosuppressive agent other than those associated with Progressive Multifocal Leukoencephalopathy (PML) such as natalizumab, rituximab, efalizumab, alemtuzumab, or mycophenolate?